1. Field of the Invention
The present invention relates generally to hermetically sealed fiber optic components, and more particularly to a method of manufacturing low-temperature hermetically sealed optical fiber components.
2. Description of the Prior Art
Recent developments in optical communications have generated a need for special devices which require a hermetic housing to protect the optical devices from contamination by elements in the outside atmosphere such as moisture. Inasmuch as optical signals exit or enter the hermetic housing via optical fibers 10, some means to hermetically seal fiber 10 to the housing is required. For most applications, a satisfactory seal should be inexpensive and reliable, and optical fiber 10 should undergo no significant change in optical or mechanical properties due to the construction of the seal.
FIG. 1 illustrates a schematic of a typical plastic-buffered glass core/clad optical fiber 10 which represents the vast majority of optical fibers presently being commercially produced. It consists of a glass core 12 which is surrounded by a glass cladding 14. The index of refraction difference between the two glasses 12 and 14 allows optical fiber 10 to transmit light with minimal losses. A plastic buffer 16 is placed on the surface of glass cladding 14 immediately after its fabrication. Plastic buffer 16 is required to protect glass cladding 14 from abrasion and moisture since the tensile strength of a glass fiber is dependent on minimizing the formation of surface flaws. Any abrasion of glass cladding 14 will greatly decrease the fiber's strength and its ultimate utility. Moisture is also detrimental to the tensile strength of optical fiber 10 since water can exaggerate surface flaws and also lower the tensile strength of optical fibers 10. These are the principal reasons why plastic buffer 16 is used to coat optical fibers 10. Any removal of plastic buffer 16 results in an optical fiber 10 that is very vulnerable to breakage and failure.
In prior art processes, the hermetic seal was formed onto a bare glass fiber 10 or a metal (gold)-coated optical fiber 10 using a high-temperature braze or sealing glass at a temperature greater than almost 800.degree. C.
For example, U.S. Pat. No. 4,119,363, by Camlibel et al., discloses a technique for forming a hermetic seal between bare optical fiber and a low melting metal. As stated above, bare fibers are susceptible to moisture and scratching as well as being mechanically weak. It should be appreciated that optical devices which may be handled roughly or may be subjected to mechanical loads require fibers which are mechanically strong. Finally, the seal which results from the Camlibel et al. disclosure does not result in a chemical bond.